mitchellh/vagrant — pull request #5030 by willdurand (2014-12-19 11:27:50+00:00)
Title: Being able to edit a file does not mean you can write in its parent directory

Interactive `sed` needs write permission on the file itself. However, it may create a backup file, which leads to the fact that the directory where the file is located must be writable as well. That is a side effect because this directory does not need to be writable.

This patch fixes this side effect by editing the file in `/tmp`, and replaces it right after.